Influence of N content on microstructure and thermal stability of Ta–N thin films for Cu interconnection

Statistical Analysis of Electromigration Lifetimes and Void Evolution for Cu Interconnects

“…Which crystal structure forms depends significantly on processing conditions. While most PVD processes lead to β-Ta films, especially when the film is deposited onto a dielectric material, careful adjustments of processing parameters as well as the use of a TaN underlayer or a CVD process were observed to produce the low resistivity α-Ta [Edelstein 2001, Donohue 2002, Hecker 2002, Demuynck 2003]. Different crystal structures within one film were found as well [Lee 1999, Kwon 2000.…”

Advanced Barriers for Copper Interconnects

“…Since an additional passivation layer on top of the Cu layer reduces the Ta diffusion [12], this process could be explained by the strong affinity between Ta and O 2 occurring in traces in the furnace. With increasing N content in the barriers, the tendency of the Ta outdiffusion decreases, as was also observed for binary Ta-N barriers [11]. Taking into account the steep increase of the resistivity of Ta-Si-N barriers with nitrogen contents above 25 at%, thus a suitable barrier system is represented by the TaSiN2 composition with still very high thermal stability and moderate resistivity properties.…”

“…Though the thermal stability of the binary W-N barriers is higher than that of a binary Ta-N barrier with 20 at% N content (cf. [11]), it is below that of ternary TaSi-N barriers. Therefore, also films deposited with additional silane flow to obtain W-Si-N barriers were evaluated.…”

“…In analogy to the case of binary Ta-N barriers, where a nitrogen addition increases the thermal stability of the barriers [11], also the ternary Ta-Si-N barriers can withstand longer anneals without crystallization compared to the TaSiN0 sample. As the first crystalline phase in Ta-Si-N films, nitrides are obtained (Ta 2 N for TaSiN1 and TaSiN2; Ta 5 N 6 for TaSiN3), which are in the case of TaSiN1 followed by a silicide (Ta 5 Si 3 firstly observed after t an = 64 h).…”

Diffusion barrier performance of novel Ti/TaN double layers for Cu metallization

“…Hence, many refractory metals and their nitrides, such as W and WN [9][10][11], Ti and TiN [7,[11][12][13][14], Ta and TaN [3,5,6,[15][16][17], have been chosen as potential diffusion barriers for Cu interconnects because of their excellent thermal stability and good electrical conductivity. Recently, the tantalum nitride (TaN) film has been widely studied in silicon devices as a diffusion barrier for Cu metallization due to its relative good barrier effect and stable structure [18][19][20]. A lot of investigations have conformed that the phase composition and microstructure of as-deposited Ta-N films depend strongly on the change in the N to Ta atomic ratio, which can be controlled by deposition process or annealing ambient [21][22][23][24].…”